1. Field of the Invention
The present invention relates to an access point device that configures a wireless LAN system with a terminal device, and a wireless channel determination/selection method for use in the access point device.
2. Description of the Related Art
With a wireless LAN system configured by an access point device and a terminal device, communications is performed through selection of wireless channels from a frequency range of 2.4 GHz, 5.2 GHz, or others, which are defined by IEEE 802.11. In the environment for the wireless LAN system to use, when there is another wireless LAN system, there needs to select a wireless channel suited for communications from many others available for use.
For the selection of a wireless channel, previously, channels available for use are scanned, i.e., sequentially selected, in the access point device, and each of the channels is checked whether or not a wireless LAN signal is included therein. As such, any channel not including the wireless LAN signal is eventually selected.
With such a previous selection method, however, the use efficiency of wireless channels is impaired. This is because if the traffic volume of a channel is a level not affecting data transmission/reception in the wireless LAN system, the channel is not selected, e.g., when a wireless LAN signal found in a channel is only a beacon frame, which is provided by another access point device at regular intervals.
Exemplified here is a case where three channels of 1, 2, and 3 are wireless channels available for use, and there are one or more wireless LAN systems for these channels 1, 2, and 3. The data transmission/reception is large in volume in channels 1 and 2, and no data transmission/reception is performed in the channel 3. In this case, the channel 3 is desirably selected as being optimum for communications in the wireless LAN system. However, with the above previous selection method, the channel 3 is not always eventually selected because the existence of a wireless LAN signal is an only determination factor to determine and select a wireless channel.
For betterment, Patent Document 1 (JP-A-2002-271336) describes a method of a terminal device issuing a request to an access point device for a wireless channel change based on monitoring of an error ratio observed to a transmission/reception packet in the terminal device.
Patent Document 2 (JP-A-2005-142777) describes a method of an access point device changing a wireless channel based on its monitoring of an error ratio observed to a packet transmitted thereby.
Patent Document 3 (JP-A-2002-158667) describes a method of selecting a clear wireless channel based on an access point device checking whether there is a wireless LAN signal in wireless channels, and measuring the volume of a packet traffic in each of the wireless channels.